First off, Mozilla believes in the service. Mozilla itself gets funding from donations and corporate backing (I think). The cost of bandwidth is small compared to other file share sites in that the files stored are temporary. The transient nature of the files means that the max storage space needed is relative to the concurrent number of users. Bandwidth also. That means sans a very clever DDoS their expenses should be manageable compared to say Google Drive, Dropbox, or MS One Drive.

I remember sending a signed PDF via Firefox Send and was at first horrified when I realized I couldn't get the file back after 24 hours but then relieved knowing that the recipient got it and then it disappeared from the internet. Very cool!

One of their KPIs is: "Percent of users who have or create an FxAccount via Send, Why: representation of % of any service users who might be amenable to an upsell"

From this it seems that their moneymaker is the new Firefox account creations that will be driven by this service, to whom they can then upsell. But it doesn't state what they are trying to upsell. Anyone got any idea what that might be?

I would imagine that to be Firefox itself and Firefox for Android/iOS. I've seen people easily set up syncing on Google Chrome because they already have a Google account to which they might even already be logged in, while they're completely unaware that Firefox has a similar feature.

If you already have a Firefox account, the barrier to using Firefox Sync is lower, and with that, the barrier to using Firefox for Android/iOS is lower.

We believe that a privacy respecting service accessible beyond the reach of Firefox will provide a valuable platform to research, communicate with, and market to conscious choosers we have traditionally found hard to reach.

We will know this to be true when we can conduct six research tasks (surveys, A/B tests, fake doors, etc) in support of premium services KPIs in the first six months after launch.

Ah. In that case, I seem to recall they performed user research among users of their browsers that uncovered that sending files to others was still a major pain point. It's also a way in to promote a Firefox account, and Firefox in general.

Of course Mozilla's not in it for the money, so there's not a direct line from Send to more revenue. Firefox is their main tool to protect the open web, and Send is a way to get more people to use that. And of course, being able to send files encrypted is good for the web as well.

Indirectly, it is primarily financed by the search engine deal in Firefox.